Software & DevOpsDone with custom-built or unnamed agent Sep 20, 2026
Port the Copilot runtime to Rust agentically
Microsoft reportedly used agents to port its Copilot runtime to Rust for $120K, according to the headline.
- What They Did
- Microsoft used Copilot, driven by several LLMs picked for their strengths, to rewrite the TypeScript Copilot runtime in Rust one module at a time. The port was a direct replacement and did not restructure the runtime. On the 30,000-line session.ts, one session read the docs, spawned 15 child sessions in separate worktrees, and had them coordinate with each other.
- How It Went
- Agents turned 430,000 lines of TypeScript into 800,000 lines of Rust over 14.5 weeks and 135+ releases. A benchmark ran 15.9x faster and memory fell from 1,383 MB to 126 MB, but a few dozen regressions appeared.
- Worth Knowing
- Cost was about $120K in tokens plus roughly three weeks of a developer's time. Compiling did not mean correct, so regressions still got through.
Try it yourself with custom-built or unnamed agent
I want to port [component or module] in [repo path] from [source language] to Rust using an agentic workflow. Start by reading the code and proposing a phased porting plan with test checkpoints, and wait for my approval. Then port one module at a time, keeping the existing tests passing, and finish with a summary of what's ported, what's left, and an estimate of effort.
Do this with a skill.
These SkillShop playbooks do this exact job.